In conventional frame construction, the framing for the exterior walls and roofs are covered with a sheathing material, such as plywood or oriented strand board (OSB). A finish siding or roofing material is applied over the sheathing material. A common problem with this type of construction is the infiltration of water through the finish siding of roofing material into the wall structure or roof structure. Accumulation of moisture within the structure can have adverse effects on the structure. Water may cause materials to warp and swell, promote growth of mildew and mold, and cause wood to degenerate and rot. Growth of molds can have serious health consequences and the development of rot can compromise the integrity of the building structure.
To prevent water damage, it is common practice to use a water barrier to prevent infiltration of moisture into exterior sheathing materials. Materials commonly used for moisture protection include asphalt impregnated felts and spun-bonded polyolefin sheeting, e.g., Tyvek. Asphalt-impregnated felt material may become saturated when exposed to water for prolonged periods. Polyolefin materials, on the other hand, are designed to pass water vapor while preventing the passage of bulk water. Without air circulation, however, condensed water may be trapped between the polyolefin material and sheathing. Consequently, conventional building materials and construction methods may not be adequate in some circumstances to allow sheathing materials to fully dry out.